About 50 high-emitting polluters would pay two-thirds of the government's carbon tax take, Climate Change Minister Greg Combet told the National Press Club as he hinted at a carbon price at the lower end of predictions.


He told journalists that the government was using compensation agreed under the dumped Carbon Pollution Reduction Scheme as its basis for current negotiations with industry.


In a move to reassure business, Mr Combet said the Gillard government was committed to providing substantial transitional assistance to emissions-intensive, trade exposed industries.


But - taking a $20 carbon price - he said the average price impact on a tonne of steel would be about $2.60 out of an $800 per tonne price.


He said the tax would raise the price of aluminium from about $2500 a tonne to $2518.70.


"In other words, the carbon cost relating to the core pollution activity for steel would be one-third of 1 per cent of the value of a tonne of steel and three-quarters of 1 per cent of the value of a tonne of aluminium," he said.


In a recent paper, the government's climate change adviser Ross Garnaut suggested a carbon price in the $20 to $30 range.


Mr Combet also confirmed more than half of the carbon tax's revenue would be used for permanent assistance for millions of households.


He said the tax would be levied on 1000 of Australia's biggest polluters, but the largest impact would be on the top 50.


"When you exclude sectors that will not be covered by the carbon price, the 50 largest polluters will be responsible for around two-thirds of carbon liabilities," Mr Combet said.